Let's agree that there is not a static surface anywhere on planet earth. Everything is vibrating / moving against everything else. Therefore there is a flaw with @dover 's airbag / mattress analogy. The purpose of the optical table or any such devices is to counteract the vibration from the floor surface with its own vibration. The net result is less vibration. It cannot be zero vibration, just less. The lesser vibration will allow instruments sitting on top of it to perform highly accurate measurements. The accuracy level required and achieved is many order of magnitude greater than the pitiful toys we play with called the turntable. we can debate the efficacy of the particular optical table in question. But the principle behind these devices is sound, no?
Not to belabor the point, but a more accurate analogy : the mattress is analogous to the floor. The optical table rest on the mattress. With the oprical table functioning properly, the person on top of the table should be able to make a more accurate measurement of the ceiling height.
